Hydrodynamic brake

ABSTRACT

The present invention relates to a hydrodynamic brake which comprises a stator, a rotor, a toroidal space defined by the stator and the rotor, a medium which is intended to be supplied to the toroidal space when the brake is activated, and a multiplicity of components for allowing regulation of the flow of the medium to and from the toroidal space. The hydrodynamic brake incorporates a structure with a multiplicity of recesses which each have an opening in a substantially common plane and each is intended to accommodate one of the components.

BACKGROUND TO THE INVENTION, AND STATE OF THE ART

The invention relates to a hydrodynamic brake and particularly tostructures housing components of the brake.

Hydrodynamic brakes such as retarders incorporate not only a stator anda rotor but also a number of components which are necessary for ensuringproper functioning of the retarder. Such components may comprise valvesof various kinds which regulate the oil flow in a number of pipecircuits for the retarder. Another component is a pump (which may be agear pump) which is required for transferring oil from an oil sump. Afurther component is an accumulator which caters for rapid filling ofthe retarder when necessary. Conventional retarders are usuallyconstructed in such a way that the majority of said components arerelatively dispersed in the retarder. This renders the fitting andservicing of components of a conventional retarder laborious andrelatively complicated.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a hydrodynamic brakewhich is so constructed that the majority of the brake's constituentcomponents are very easily accessible so that fitting and servicingbecome easy and take relatively little time.

This object is achieved with the hydrodynamic brake of the inventionwhich relates to a hydrodynamic brake which comprises a stator, a rotor,and a toroidal space defined by the stator and the rotor. A medium isintended to be supplied to the toroidal space when the brake isactivated. A multiplicity of components allow regulation of the flow ofthe medium to and from the toroidal space. The hydrodynamic brakeincorporates a structure with a multiplicity of recesses each having anopening in a side thereof, e.g. in a substantially common plane and eachrecess is intended to accommodate one of the components. The fact thatthe hydrodynamic brake comprises a structure with a multiplicity ofrecesses which have openings arranged in a substantially common planerenders these components very easily accessible. Dismantling thehydraulic brake for access to such a plane which incorporates recessesfor the various components can be made very simple and involve only asmall number of working operations. It becomes easy to remove thecomponents from the recesses and check them and, where necessary,substitute new ones. The fitting and servicing of the componentsarranged in such recesses can thus be done quickly and easily.

According to a preferred embodiment of the present invention, saidstructure is incorporated in a first element of the hydrodynamic brake,and a second element of the hydrodynamic brake is detachably fittablealong a connecting region to the first element so that said elements ina fitted state form a housing which entirely surrounds said components.Access to said plane is then by removing the second element, which canbe done in a relatively uncomplicated manner by using suitablefastenings. With advantage, the connecting region has an extent in saidplane. Removal of the second element provides immediate access to saidspaces which accommodate the various components. A gasket is preferablyarranged in the connecting region between said first and second elementsof the housing. Such a gasket results in a sealed housing whichsurrounds said components and prevents the enclosed medium from leakingout.

According to another preferred embodiment of the present invention, atleast one of said components is a valve means. A hydrodynamic brakeincorporates a number of valves of various kinds which are necessary forthe functioning of the hydrodynamic brake. With advantage, substantiallyall such valves are arranged in spaces which have an opening in saidplane. Such valves may comprise a regulating valve, a safety valve andcheck valves with various functions. One of said components may be agear pump. A gear pump is of simple design and can with advantage bearranged in such a space. Another of said components may be anaccumulator. In this case the recess may be of an appropriate shape forstoring the medium at high pressure.

According to another preferred embodiment of the present invention, thehydrodynamic brake incorporates a storage space for the medium. As thefirst element and the second element form a completely sealed enclosureof said components, it is advantageous that a storage space for themedium be incorporated in said housing. The medium is preferably an oiland the storage space may therefore be described as an oil sump. Withadvantage, the first element incorporates the stator and the rotor, andthe second element is of cover-like design. In this case the cover-likesecond element may be easily detachable from the first element so as toprovide access to said recesses. The first element and the secondelement may be mouldings made of a suitable material. The first elementmay have moulded recesses with a shape entirely adapted to the specificcomponents to be accommodated in the recesses. The first elementpreferably incorporates at least one duct to allow transfer of themedium. The first element may incorporate a structure which comprises,adjacent to the recesses, a multiplicity of readymade ducts for transferof the medium. There is thus substantially no need to arrange anyseparate ducts for allowing transport of the medium in the firstelement.

BRIEF DESCRIPTION OF THE DRAWING

A preferred embodiment of the invention is described below by way ofexample with reference to the attached drawing, in which:

FIG. 1 depicts a section through a retarder according to the presentinvention,

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 depicts a hydrodynamic brake in the form of a retarder of apowered vehicle. The retarder comprises a stator 1 and a rotor 2. Thestator 1 has an annular shell 3 with a multiplicity of blades 4 arrangedat uniform spacing along the annular shell 3. The rotor 2 is ofcorresponding design with an annular shell 5 which incorporates amultiplicity of blades 6 likewise arranged at uniform spacing along theannular shell 5. The respective shells 3, 5 of the stator 1 and rotor 2are coaxially arranged with respect to one another so that they togetherform a toroidal space 7. The rotor 2 incorporates a shaft portion 8which is firmly connected to a rotatable shaft 9. The rotatable shaft 9is itself connected to an appropriate driveshaft of the vehicle'sdriveline. The rotor 2 will thus rotate together with the vehicle'sdriveline.

The retarder depicted in FIG. 1 incorporates a housing which comprises afirst element 10 and a second element 11. The first element 10incorporates a body in which inter alia the stator 1 and the rotor 2 arearranged. The second element 11 is of cover-like design and can befitted detachably along a connecting region 12 to the first element 10so that in a fitted state they form a closed housing. In the connectingregion 12, a gasket 13 is arranged so that the housing forms a sealedenclosure. The first element 10 incorporates a multiplicity of recesses14–23 which each have an opening in a substantially common plane Arepresented by the broken line A—A in FIG. 1. The connecting region 12of the first element 10 and second element 11 also has an extent in saidplane A.

The recesses 14–23 are each designed to accommodate a component whichforms part of the retarder. The shape and size of the recesses 14–23 areadapted to the respective specific components which they accommodate. Afirst such recess 14 accommodates a first check valve 24. A secondrecess 15 accommodates an outlet check valve 25. A third recess 16accommodates a gear pump 26. A fourth recess 17 accommodates a secondcheck valve 27. A fifth recess 18 accommodates a dump (rapid emptying)valve 28. A sixth recess 19 accommodates a regulating valve 29. Aseventh recess 20 accommodates an inlet check valve 30. An eighth recess21 accommodates a filling valve 31. A ninth recess 22 accommodates anintake valve 32 for filling an accumulator 33. A tenth recess 23accommodates said accumulator 33. The first element 10 and the secondelement 11 thus form a sealed housing which incorporates an oil sump 34for storage of oil.

The retarder incorporates a first pipe circuit 35 with a first portion35 a which leads the oil from an outlet from the toroidal space 7 to theoutlet check valve 25. A second portion 35 b of the first pipe circuitleads the oil from the outlet check valve 25 to a heat exchanger 36 tocool the oil. A third portion 35 c of the first pipe circuit leads thecooled oil to the inlet check valve 30 or alternatively to theregulating valve 29, depending on whether the retarder is or is notactivated. A fourth portion 35 d of the first pipe circuit leads the oilto an inlet to the toroidal space 7. The retarder incorporates a secondpipe circuit 37 with a first portion 37 a via which the oil is drawnfrom the oil sump 34 to the gear pump 26. A second portion 37 b of thesecond pipe circuit 37 leads the oil to the first check valve 24 and thesecond check valve 27. When the retarder is not activated, the oil isled via the first check valve 24 and a third portion 37 c of the secondpipe circuit to the second portion 35 b of the first pipe circuit. Ifthe retarder is activated, the oil is led instead via the second checkvalve 27 and a fourth portion 37 d of the second pipe circuit to aninlet to the toroidal space 7. The retarder also incorporates a thirdpipe circuit 38 which connects the accumulator 33 to a fourth portion 35d of the first pipe circuit. The third circuit 38 incorporates thefilling valve 31 and the accumulator's intake valve 32. The firstelement 10 of the housing incorporates, adjacent to the recesses 14–23,occupied ducts which form part of the aforesaid pipe circuits 35, 37,38.

A first control valve 39 is intended to control, by means of a controlpressure, the operation of the safety valve 18 so that the toroidalspace 7 can be quickly emptied of oil when necessary. A proportionalvalve 40 is intended to control, by means of a control pressure, theoperation of the regulating valve 19 in order to activate the retarderand regulate the retarder's braking action. A second control valve 41 isintended to control, by means of a control pressure, the operation ofthe accumulator 33 so as to fill the toroidal space quickly with oil inorder to effect a rapid braking action of the retarder. All of thesethree control valves 39, 40, 41 and the heat exchanger 36 are situatedoutside the housing.

When the vehicle's driver does not require the vehicle to be subjectedto any braking action, the proportional valve 40 supplies no controlpressure to the regulating valve 29, which opens fully so that any oilin the third portion 37 c of the first pipe circuit drains away, via apassage 42, to the oil sump 34. This means that no oil runs past theinlet check valve 30, which requires relatively high oil pressure for itto open and lead oil to the toroidal space 7. As in this situation nooil is led to the toroidal space 7, substantially no braking action iseffected other than a minor undesired braking action due to a so-calledno-load loss caused by the rotor circulating the air present in thetoroidal space 7.

The driveshaft 9 also drives the gear pump 26 which continuously pumpsoil from the oil sump 34 during operation of the vehicle. From the gearpump 26, the oil is led at a positive pressure to the second portion 37b of the second pipe circuit. The first check valve 24 here has a springwith preloading such that it opens at a positive pressure of about 0.5bar. The second check valve 27 has a spring with preloading such that itopens at a positive pressure of about 2 bar. When the regulating valve29 is open, there is substantially no positive pressure in the firstpipe circuit 35. This means that in the second portion 35 b of the firstpipe circuit there is no positive pressure which would otherwiseincrease the opening pressure for the first check valve 24. As the firstcheck valve 24 opens at a lower pressure than the second check valve 27,the oil transferred from the oil sump 34 by the gear pump 26 is only ledvia the first check valve 24 and the third portion 37 c of the secondpipe circuit to the second portion 35 b of the first pipe circuit, whichis thus situated after the toroidal space 7 in the direction of flow ofthe oil. Thereafter the oil is led back to the oil sump 34 via the heatexchanger 36, the third portion 35 c of the first pipe circuit, and theregulating valve 29.

When the vehicle's driver requires the vehicle to be subjected to abraking action, the proportional valve 40 supplies the regulating valve29 with a control pressure which is greater than the preloading of theinlet check valve 30. The second control valve 41 activates theaccumulator 33 so that the latter, via the third pipe circuit 38 and thefilling valve 31, leads oil at high pressure to the fourth portion 35 dof the first pipe circuit and to the toroidal space 7. The accumulator33 initiates oil supply by means of a positive pressure to bring aboutrapid filling of the toroidal space 7 and thereby effect a correspondingrapid braking action of the retarder. After the circulation of the oilin the toroidal space 7, the oil is led out at high pressure via anoutlet from the stator 1 to the first portion 35 a of the first pipecircuit The outlet check valve 25 is opened by the high oil pressure andthe oil is led to the second portion 35 b of the first pipe circuit. Atthis stage the oil is at a positive pressure of at least 5 bar. The oilin the second portion 35 b of the first pipe circuit is also led intothe third portion 37 c of the second pipe circuit and exerts there apressure action urging the first check valve 24 towards a closedposition. The opening pressure required for the first check valve 24will thus be higher than the corresponding opening pressure for thesecond check valve 27 which had a preloading of about 2 bar. This meansthat all of the oil transferred by the gear pump 26 from the oil sump 34will be led via the second check valve 27 and the fourth portion 37 d ofthe second pump circuit to an inlet to the toroidal space 7.

The inlet to the toroidal space 7 is with advantage arranged centrallyin the toroidal space 7.1. In the central part of the toroidal space arelatively low pressure prevails in substantially all operating states.Using a separate pipe portion 37 d to supply the oil from the oil sump34 at atmospheric pressure to the toroidal space 7 means that this oilneed not be pumped up to the high pressure which prevails in the fourthportion 35 d of the first pipe circuit. A less expensive gear pump 26with a smaller pump capacity can therefore be used. The fourth portion37 d of the second pipe circuit may also be of relatively simple designsince it need only be dimensioned to carry oil at a relatively smallpositive pressure.

The oil is led from the second portion 35 b of the first pipe circuit tothe heat exchanger 36, in which it is cooled. The braking action of theretarder is regulated by the control pressure from the proportionalvalve 40. The position of the regulating valve 29 is adjusted by meansof the control pressure from the proportional valve 40 so that a certainproportion of the cooled oil after the heat exchanger 36 is led back tothe oil sump 34, while the remainder is led past the inlet check valve30 to the toroidal space 7. The result is regulation of the amount ofoil circulating in the toroidal space 7 so as to effect a desiredbraking action.

The fact that the retarder incorporates a structure with a multiplicityof recesses 14–23 which have openings arranged in a substantially commonplane A renders these components 24–33 very easily accessible. Removingthe cover-like second element 11 from the first element 10 providesimmediate access to the various components 24–33 arranged in therecesses 14–23, without further dismantling work, since the openings ofall the recesses 14–23 are situated in a substantially common plane A.This means that the components 24–33 can easily be taken out andserviced or replaced as necessary. In a fitted state, the gasket 13 inthe connecting region 12 between the first element 10 and the secondelement 11 prevents oil in the sump 34 from leaking out. The elements10, 11 may be made of a suitable material by, for example, a mouldingprocess. The recesses 14–23 may be of specific shape and sizeappropriate to the respective components 24–33 to be accommodated in thespace 14–23.

The invention is in no way limited to the embodiment described but maybe varied freely within the scopes of the claims.

1. A hydrodynamic brake comprising: a stator which has an annular shellwith a multiplicity of blades supported in the respective shell; a rotorwhich has a corresponding annular shell with a number of blades alsosupported in the respective shell; the annular shells of the rotor andthe stator are so shaped and arranged that they form a toroidal space inwhich the blades extend for receiving a medium which is intended to besupplied to the toroidal space for effecting a braking action betweenthe rotor and the stator when the medium is supplied to the space; anumber of components for allowing regulation of the flow of the mediuminto or out of the space; and a housing having a first sideaccommodating the rotor and stator and including at least three recessesformed in the first side, wherein each recess provides an opening toaccommodate one of the components and including a second side which isdetachably connected to the first side along a connecting region so thatthe first side and second side together form the housing and surroundthe rotor, the stator, and the components and enclose the recesses ofthe first side of the housing.
 2. A hydrodynamic brake according toclaim 1 further comprising a gasket arranged in the connecting regionbetween the first and second sides of the housing.
 3. A hydrodynamicbrake according to claim 1, wherein one of the components is a valve. 4.A hydrodynamic brake according claim 1, wherein one of the components isa gear pump.
 5. A hydrodynamic brake according to claim 1, wherein oneof the components is an accumulator.
 6. A hydrodynamic brake accordingto claim 1, wherein the hydrodynamic brake incorporates a storage spacefor the medium.
 7. A hydrodynamic brake according to claim 1, whereinthe first side of the housing incorporates the stator and the rotor andthe second side of the housing is a cover over the first side.
 8. Ahydrodynamic brake according to claim 1, wherein the first side of thehousing incorporates in its structure at least one duct to allowtransfer of the medium.
 9. A hydrodynamic brake according to claim 1,wherein each of the components is received in one of the recesses to beaccessible from the side of the housing.
 10. A hydrodynamic brakeaccording to claim 1, wherein the first side of the housing with therecesses therein is in a substantially common plane.
 11. A hydrodynamicbrake according to claim 10, wherein the connecting region is adjacentto the common plane.